Joba Chamberlain’s Massive ERA

Naturally, the Yankees were in on the Dan Haren discussions until the very end. Supposedly, the package that they were putting together centered around Joba Chamberlain. Given that the Diamondbacks eventually took the Joe Saunders and prospects package put together by the Angels, one has to assume that Arizona simply wasn’t impressed by Joba Chamberlain. Truly, relievers with a 5.86 ERA typically aren’t centerpieces in trades for aces, but Joba isn’t having a typical season this year.

We can quickly point out that Chamberlain has a 3.02 FIP and a 3.48 xFIP, both very solid numbers out of a relief pitcher, especially given that Chamberlain has entered games in high leverage situations this season: his gmLI (average entrance LI) is 1.31, a typical number for a setup man. He’s not showcasing the ridiculous ability to miss bats that he did when he first came up, but his K-rate is still over a batter per inning, and a walk rate below four is plenty to make a good reliever.

It just hasn’t come together this season, as far as results. Chamberlain is getting killed on contact, as hitters have a .393 BABIP against him. It’s not like hitters are just roping line drives, either – the line drive rate is slightly down this season, and just under half of all batted balls against Chamberlain have been ground balls. If anything, a low IFFB rate of 2.3% would explain some of this success, but not nearly all of it. tERA, which is based on batted balls, still rates Chamberlain highly, at 3.28.

The difference between Joba’s 5.86 ERA and his 3.04 FIP is 13.5 earned runs in his 43 innings pitched so far – and that’s ignoring the fact that a big portion of Chamberlain’s inflated ERA is due to the fact that he would have gotten more outs if his BABIP was closer to average. These 13.5 runs can be largely attributed to two splits.

In 43 innings, a few bad pitches with runners on can drastically inflate your ERA. Joba Chamberlain has pitched extremely well this year by almost every metric. He has struck out over 10 batters per 9 innings in high leverage situations. Even if he’s not living up to his original hype, he is still a valuable player. The Diamondbacks shouldn’t have been scared away by his mammoth ERA, nor should the Yankees or their fans worry about Joba’s future, particularly in the bullpen.